This project is designed to evaluate the relationship between the metabolism of the inositol-containing phopholipids and the secretion of insulin from the stimulated rat pancreatic islet. The carbohydrate and amino acid substrate as well as the ionic requirements for the phosphoinositide response will be evaluated. The subcellular localization of phosphatidylinositol and the changes in its localization following stimulation will be studied by means of radioautography. The surface charge characteristics of isolated insulin granules obtained from stimulated and unstimulated islets will be evaluated by microelectrophoretic techniques. The ability of isolated islets to actively transport radioactive myo-inositol into the intracellular space, and the effect of carbohydrate stimulation upon this phenomenon will be evaluated with double-label techniques. The enzymes concerned with the incorporation of myo-inositol into phospholipids, its subsequent phosphorylation, and its hydrolysis will also be studied. Finally, the pattern of incorporation of arachidonic acid into islet phospholipids, the response of those lipids to carbohydrate stimulation, and the pattern of release of the various prostaglandins from pre-labeled islets will be studied.